This invention relates to improvements in the manufacture and construction of centrifugal blower wheels, and it is especially concerned with blower wheels of the forwardly curved type, i.e. wherein the individual blades have their concave sides facing in the direction of rotation of the wheel. The prior art with which applicant is most familiar comprises United States patents issued to his assignee over the past 30 years, particularly Wilken U.S. Pat. Nos. 2,537,805, 2,628,419, 2,628,659 and 2,852,182, Wentling U.S. Pat. Nos. 3,165,258, 3,211,364 and 3,385,511, and Ranz U.S. Pat. No. 3,737,966, and the blower wheels manufactured and sold thereunder.
In that past commercial practice, while some wheels have been manufactured with the end rings resistance welded to the blades, the end rings were of one or another special configuration to provide small areas of contact with the blades during welding, and the more common practice has been to employ end rings which were spun into overlapping relation with flanges formed radially outwardly from the ends of the blades. This practice is wasteful of the sheet metal scrap which is produced from the areas between the flanges of adjacent blades as they are blanked out of sheet stock, and it also has a high initial tooling cost for the dies which blank and form the flange portions of the blades.
These facts have resulted in a common practice of producing blades of the same angular dimensions for all sizes of wheels of a given type, in order to minimize the tooling cost, and also to limit the angular extent of the individual blades to substantially less than 90.degree., since the wider the blade, the greater amount of scrap around its flange portions. This in turn made it necessary to increase the number of blades for each successively larger diameter wheel, with the result that wheels made by that conventional practice by applicant's assignee have incorporated as many as 56 blades for a 25-inch diameter wheel and 66 blades for a 30-inch wheel.